-able vs -eable is not about GB or US spelling

The grammar rule is that the final silent "e" of the root verb is
dropped, except for root verbs ending in "ce" and "ge". The rule is
the same in British and American English, and so is actual usage
according to the Google Ngram Viewer:
https://books.google.com/ngrams/graph?content=writable%2Cwriteable&year_start=1900&year_end=2019&corpus=en-GB-2019
https://books.google.com/ngrams/graph?content=writable%2Cwriteable&year_start=1900&year_end=2019&corpus=en-US-2019

We could of course drop this rule from our typo dictionaries, on the
basis that it is not widely followed in practice. However, we should
the drop all -eable entries, not just this single entry.

codespell_lib/data/dictionary.txt

@@ -61167,6 +61167,7 @@ wresters->wrestlers
 wrestlin->wrestling
 wriet->write
 wriets->writes
+writeable->writable
 writebufer->writebuffer
 writechetque->writecheque
 writed->wrote, written, write, writer,

codespell_lib/data/dictionary_en-GB_to_en-US.txt

@@ -453,4 +453,3 @@ visualised->visualized
 visualiser->visualizer
 visualises->visualizes
 visualising->visualizing
-writeable->writable